1. Field of the Invention
The present invention relates to orthopedic surgical instruments and surgical methods and more particularly relates to an improved method and apparatus for installing a knee prosthesis with instrumentation that allows a surgeon to rotate a tibial trial prothesis about the patient's intramedullary canal axis with a lever while the patient's knee is flexed through a full range of motion and with a corresponding femoral trial prosthesis in place.
2. General Background
In knee joint replacement surgery, a surgeon typically affixes two prosthesis components to the patient's femur and tibia. These replacement components are typically known as the femoral component and the tibial component.
The femoral component is placed on a patient's distal femur after the surgeon makes a plurality of surgical cuts. One common type of femoral prothesis has a J-shape. A femoral prosthesis is usually metallic, having a highly polished outer femoral articulating surface.
A common type of tibial prosthesis uses a laterally extending tray that is shaped to conform to the patient's proximal tibia after the proximal tibia has been cut transversely by the surgeon. The tibia prosthesis also includes a stem or plug that extends generally perpendicular to the tray and from the center of the tray. The stem is placed in a surgically formed opening that extends into the patient's intramedullary canal from the transverse cut formed on the proximal tibia.
A plastic, polymeric insert is attached to the tibial tray. This insert provides a tibial articulating surface that articulates with the femoral articulating surface as the patient's tibia moves through a full range of motion with respect to the patient's femur.
One of the problems with knee joint replacement surgery is that of accurately fitting the patient. Each patient has a different bone structure and geometry. Even though the surgeon uses x-rays to study a particular patient's anatomy at the knee, the surgeon does not have a perfect appreciation of the patient's anatomy until after the knee has been surgically exposed and the surgeon begins to make cuts on the femur and the tibia.
Knee prosthetic components are not available in infinite sizes. The surgeon must examine the patient's anatomy, make the requisite surgical cuts and install prosthesis components that fit.
A number of tibial components have been patented that relate to tibial components having a tray, a plastic insert with articulating surface, and a stem portion that provides initial fixation when the prosthesis is implanted. Other patents have issued that relate to cutting instrumentation for preparing the patient's proximal tibia to receive a tibial prosthetic insert as part of knee joint replacement surgery.
The Murray U.S. Pat. No. 4,016,606 discloses a knee prosthesis that includes a tibial component with a tray and with a stem adapted to be received in a longitudinal bore in the patient's femur. The stem has one end that is integral with a depending generally spheroidal surface having generally the same radius as the radius of the spheroidal depression in the insert.
In the Chiarizzio U.S. Pat. No. 4,601,289 there is disclosed a femoral trial prothesis/rasp assembly used in hip implant surgery. The assembly includes a handle that grips the combination trial prothesis/rasp in a secure manner by clamping over and locking on to a post on the trial prothesis/rasp which later serves as a mounting piece for a femoral prothesis head used in trial reductions.
A modular tibial prosthesis is disclosed in the Shaw U.S. Pat. No. 4,938,769. The Shaw patent discloses a tibial prosthesis for use during a total knee arthroplasty procedure which includes a modular two part tibial component comprising an in-bone anchorage assembly to which is removably attached a tibial tray adapted to receive and retain a bearing insert. Removal of the tray permits access to the interface between the bone and anchorage assembly in the event removal or revision are necessary. In preferred embodiments, the invention affords hybrid fixation of the tibial prosthesis in that bone cement for immediate fixation and adaptation for longer term bone ingrowth are featured. Shaw also discusses the use of porous coatings to enhance fixation.
U.S. Pat. No. 4,938,769 issued to James Shaw discloses an end bone anchorage assembly for a tibial prosthesis that includes an axially elongated central stem and a plurality of elongated fixation pegs spaced from the stem. The stem and the pegs have proximal and distal ends. The proximal ends of the stem define an attachment table. A plurality of structural links interconnect the pegs and the stem. Means is provided for removably attaching a tibial tray to the assembly wherein each of the pegs is connected to the stem by the structural link.
A tibial component for a replacement knee prosthesis is disclosed in the Lawes et al. U.S. Pat. No. 5,080,675. Lawes discloses a tibial component for a replacement knee prosthesis comprising a tibial tray for connection to a suitably prepared tibia, the tray carrying fixed lateral and medial condylar bearing components. Only the medial component has a shock absorber located beneath it.
U.S. Pat. No. 5,137,536 issued to Tomihisa Koshino describes a tibial component for an artificial knee joint. The tibial component includes a plate section having an upper surface and a pair of bearing surfaces parts that are adapted to be in sliding contact with a femoral component. A stem portion extends downwardly from a lower surface of the plate section. A pair of blade like members extend obliquely and posteriorly from the stem. The plate section has a lower surface with a plurality of elongated grooves for improving affinity with respect to the surrounding bone, the grooves including a first group of grooves and a second set of group of grooves extending perpendicularly to the first group of grooves.
An example of a modular tibial support is seen in the Elias U.S. Pat. No. 5,246,459 entitled "Modular Tibial Support Pegs for the Tibial Component of a Prosthetic Knee Replacement System". The Elias Patent discloses a modular tibial support peg operable to secure a tibial component of a knee joint prothesis to a tibia having a groove. The modular tibial support peg includes a cylindrical body with a ridged outer surface operable to engage the groove in the tibia. The modular tibial support peg further includes a plurality of spikes extending inferiorly from the cylindrical body. The spikes are operable to engage the tibia at the inferior end of the groove.